1. Field of the Invention
The present invention relates to a light source of a non-self-luminous display device and in particular relates to a liquid crystal display device that includes a backlight that is disposed with a light guide plate and uses LEDs as light emitting elements.
2. Description of the Related Art
In recent years, liquid crystal display devices are being heavily used as display devices. In particular, liquid crystal display devices are used in display portions of portable devices because they are thin, lightweight, and save power.
However, liquid crystal display devices require illuminating means because they are not self-luminous. Among illuminating devices that are commonly used in liquid crystal display devices, a planar illuminating device called a backlight is prevalent. Conventionally, cold cathode fluorescent tubes are used for the light emitting elements (also called light sources) of a backlight, but in recent years, light emitting diodes (LEDs) are also being used as the light emitting elements.
A plate-shaped light guide plate is disposed in the backlight. The material of the light guide plate is a transparent resin or the like, and light that has been made incident on the light guide plate from the light emitting elements propagates through the light guide plate. Reflecting/scattering members such as grooves, projections or printed materials are disposed in the light guide plate. Because of these reflecting/scattering members, the light that propagates through the light guide plate is emitted toward a liquid crystal panel.
Some of the light whose traveling direction has changed because of the reflecting/scattering members is emitted to the outside of the light guide plate from the bottom surface of the light guide plate. A reflection sheet is formed on the bottom surface side of the light guide plate, and the light that has been emitted from the bottom surface is reflected toward the light guide plate by the reflection sheet toward the liquid crystal panel.
In JP-A-11-329034, there is description of a reflecting film where plural dielectric layers with different refractive indexes are laminated. However, in JP-A-11-329034, there is no description in regard to light escape of the reflecting film. Further, in JP-A-09-197402, there is description of a reflection sheet being surface-roughened by sandblasting. However, in JP-A-09-197402, there is no description of preventing light escape of the reflection sheet by sandblasting. Moreover, in JP-A-11-281976, there is description of surface-roughening a light guide plate by sandblasting. However, in JP-A-281976 also, there is no description of preventing light escape of the reflection sheet by sandblasting.